This library require a tuning (mostly base on try/modify) and will not give a correct performance until you have tuned all 3 parameters Kp, Ki and Kd for each wheels of the robot
You must use a QE (quadrature Encoder) connected to a 16 bits timer to get proper motion control. Pins A & B of the QE must be connected respectively to pin 1 and 2 of the timer. Typicaly on Nucleo F446RE TIM3 and TIM4 are perfect to do this job. In this case simply use TIM3 or TIM4 as timer parameter.
You must also specify the number of pulses generated by the QE for a 1mm displacement of the wheel. This is the scale parameter
Outputed PWM value evolve from 1 (full PWM fortward) to -1 (full PWM backward). This value can also be found in the global variable : _PwmValue. The PWM value is based on a 1.3 m/s maximum speed.
As this motion control system is implemented in a microcontroler it is important to understand that there is a loop time for the motion control system and that this loop time MUST be constant. Kp, Ki and Kd are dependent of the loop time. Changing loop time means changing all the corrector's coefficients. Library use a Ticker to control loop time. The looptime can be set by software as long as it remain constant during the whole use of PID controler. Loop time is set to 1ms by default.
The PID is initialized with Ki = 0, Kd = 0 and Kp = 1
Increasing Kp will shorten your response time but will also create instability (at beggining overshoots, then instability).
Adding a bit of Ki will allow your system to bring to 0 the static error (ie : will make the error, between the set point and your mesurment, tend to 0) but might create instability and increase setting time.
Adding a bit of Kd will stabilize the response (with almost no bad effect, as long as Kd remains small).
The odometric position is computed by the trapezoidal integration method (approximation of a part of a circle by a trapezoid) after each program loop. Hence, odometric error increase with time.
The odometric X coordinate is the direction in front of the robot at startup. Y coordinate is the orthogonal vector in trigonometric direction (counterclockwise) refered to X, and THETA is the angle of the robot refered to X at startup
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Tuk ZeroFour
1.7.2